Center for Advanced Retinal and Ocular Therapeutics, Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania; F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania; Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania. Electronic address: ashtari@mail.med.upenn.edu. University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania. Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania. Center for Advanced Retinal and Ocular Therapeutics, Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania. Westat Biostatistics and Data Management Core, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania. Center for Advanced Retinal and Ocular Therapeutics, Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania; F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania; Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.